"Kalau mau sampai, jangan naik kereta ini."

Translation: If you want to arrive, do not take this train.

[_Kuma_]

This sentence is missing its previous context, being standalone makes it very confusing.

A more complete sentence will be:

"If you want to arrive at your destination, do not take this train."

"Kalau mau sampai tujuan Anda, jangan naik kerata ini."

[ryanotron]

Karena untuk kereta ini, hanya ada perjalanan, bukan tujuan.

[ueueueueue]

This could be useful for some British train operating companies.

[Cor665827]

How do we need to know its "if you ..." i do not see kamu or kalian.

[naylahashi]

'If you' means 'jika kamu'

[noey536981]

Indonesian, like spanish, japanese, and many other languages, often omit personal pronouns and subjects.

Oftentimes the subject is infered/implied depending on context.

If you listen to Indonesians have a casual conversation together, you'll find that they dont say kamu/kalian/kau or saya/aku/ku as much as we learn in this course.

[LydiaWoold]

is 'datang 'a more suitable choice for the word 'arrive' in this context?

[Holgast]

Ominous

[scot87252]

My wife is a native Indonesian speaker, and this makes no sense to her

[Doughdle]

kereta means car, kereta api means train

[_Kuma_]

This depends on which region you speak in. In Western Java, Indonesia, a car is referred to as "mobil".

"Kereta" is usually a shortened form of "kereta api".

If you're in Malaysia, then yes, "Kereta" is "car" in bahasa melayu as far as I know of their spoken usage. I'm not too sure about other regions in Indonesia, but I suspect the Sumatran provinces and Riau Islands, being closer to the Malaysian Peninsula, probably use "Kereta" the same way as you mentioned.